LT77 into a series 3 with existing series gearbox

[Stef.]

Hi All

I have a 1980 series 3 88 with a 200 TDI that has served me well for the last few years, however the series gearbox is getting noisy, particularly in reverse. I have the option of an early Defender with an unmolested drive train and would like to swap it out completely.

I've had a trawl around the various topics and there's loads of info, mostly on different parts of the problem, There may well be a complete article, but I've missed it!

Could someone please point me towards the right thread or give me a swift overview on likely problems, should it be possible, including shifting the engine mounts, prop shaft mods and details of where the gear sticks are likely to end up?

 

Cheers

Stef

[Snagger]

Easier to rebuild the existing box, and it doesn’t gut another classic vehicle and render that one worthless.  A Series box is easily able to handle a Tdi unless abused, so you needn’t go through the headache of chassis alterations, seat base and floor mods, custom prop shafts, replacing the differentials, recalibrating the speedo and any regulatory and insurance issues unless you are looking for more than just a reliable transmission.

[Stef.]

Hi Snagger,

Thanks for a swift reply,

 

I bought the 88 about 5 years back, in the UK, a mate fettled it and declared the 'box in it wasn't likely to make the trip to the French Pyrenees so he put a recon unit from Simmonites in it that locked up after a couple of years, I replaced it with one from Beaumonts and that's getting noisy in reverse and harder to get int the forward gears, i have to shunt it in and out of reverse a few times.

Whilst I haven't really hammered the vehicle, I live off grid up a gravel track, about 300m long with a couple of 1 in 10 slopes, one of which is around a 150 degree hair pin. Every time I go out I'm in 4x4 and once a month or so I haul up a two ton trailer load of gravel / sand.

I would also like the advantage of a higher final ratio, not necessarily for the speed but to cut the noise down ar 60 or so.

It's not really an outstanding classic, It's on a galvanised chassis that I don't want to chop that about, if it can be helped.

 

Cheers

Stef

 

 

 

[Snagger]

Those conditions should not cause any trouble to the transmission behind a Tdi - you aren’t going to be using much torque on that track.

I had a reCON engine from Simmonites back in 1994.  In my opinion, they are criminal in their activities.  Outright fraud.  So, I’m not in the least surprised their unit failed rapidly.  
 

Beaumont have a decent reputation, though.  Have you checked the man shaft nut (inside the transfer box) is tight?  That can cause the problems you describe, though it does sound like there may be an issue with the 1st/2nd synchro unit (which engages the reverse idler gear when that is selected).  Remember, to keep costs down, professional reconditioners will reuse worn parts as long as they are serviceable (well, some will reuse scrap too), so that may have already been worn and is now on the wrong side of borderline.

Doing it yourself is not difficult and saves a lot of the cost while also allowing you to be certain that everything that needs replacement has been done.  Many forum members have taken it on despite nervousness about it and have had great results, and enjoyed the process too.  You don’t need many special tools, just a socket set, torque wrench and circlip pliers.

But check the main shaft but first and give it a complete oil change before you get stuck in.

[Stef.]

Hi Snagger

Ok, you're talking me around, well, a bit.....

I'll check as suggested.

I've got the first 'box in the shed, covid hit as I did the change and by the time it had settled down enough to get it back to Beaumonts they'd stopped doing series 'boxes and refused to accept it against the surcharge of £300. 

I might be able to get a second hand 'box locally, if I can I'll swap out and try the rebuild route. Is there a thread on here, or a Youtube vid anyone knows of?

Finally, whilst contemplate the rebuild route, how do I get the final ration up a bit?  I've already got Disco diffs and 235 / 70 / 16 General Grabbers

Cheers Stef

 

[Bowie69]

235/85 tyres will make a little more difference to the final drive, a good and common size too. 235/70 aren't much bigger than the original 6.50s.

[Arjan]

Bonjour from the Allier !

Series box behind 200 Tdi (intercooled & tubo charged) should not be a problem is you're not trashing it.

Apart from CT issues - some do have them - you run into all kind of things you need to address when altering the gearbox.

Open / rebuild the box and put it back in.

235's do help a bit but accept it is a Series and 75 km/h is about what you can do without chaning all kind of stuff.

[FridgeFreezer]

LT77 or R380 plus LT230 in a Series is doable and stronger, but in an 88 you run out of rear propshaft - plus depending on how your galv chassis is made it may not be possible without cutting / welding.

I won't try to persuade you that a Series box can live with being worked hard behind more HP than it was designed for - diesels especially create quite lumpy torque that is rough on weak boxes. However, it could be worth investigating what's failing and if any improvements can be made (EG stronger bearings, uprated gears, quality oil, etc.) if the alternative is major surgery.

[Daan]

Here:

and here:

More here:

All on our great forum; it appears cutting the chassis is not strictly needed.

Daan

[Snagger]

17 hours ago, Daan said:

All on our great forum; it appears cutting the chassis is not strictly needed.

Daan

I think that would put tremendous strain on the front bearing and the output shaft.  It’s not a solution I’d go for.

[Daan]

If you fit the 4 x 2 kit with free wheeling hubs, it won't see much use. Has anyone tried offering up the range rover automatic bar shaft prop in this application? Not sure on the length, but the diameter is about half that of the ordinary prop.

The X-engineering handbrake can be reversed, like so, see my thread:

[Stef.]

Hi All

 

Thanks for the support and all the information, I've found a series 'box a couple of hundred K away, in Toulouse, I'm picking it up tomorrow.

 

I'll fit that over the next week or so and report back. My vague plan is to rebuild the series box I take out, so any info on rebuild kits / suppliers of parts would be welcome.

In the mean time, can I fit any other transfer box to a series box to up the final drive ratio

Cheers

Stef

[FridgeFreezer]

13 hours ago, Stef. said:

In the mean time, can I fit any other transfer box to a series box to up the final drive ratio

No, there is a high-ratio transfer kit I think but it's huge money, if memory serves @Jon White had one or at least has a strong opinion on them

[Arjan]

I suggest you talk to Landypoint.fr (Drew Brown - speaks English) for parts and gearbox overhauls in France.

 

[Daan]

It is easier to change the diffs for a different ratio. You can fit series 1 transfer box to make the low range lower to compensate for higher diffs.

[Snagger]

Syncro Gearboxes do a gearbox rebuild kit, and I think GLF Classics may too.

The best way to increase gear ratio is with an overdrive as it allows selection and deselection as convenient.  A High Ratio Transfer Case (Ashcroft Transmissions) is a little taller, more robust and a little more efficient (less moving parts and gear interfaces than ordinary box plus overdrive), but lacks flexibility.  3.54 diffs are taller than the HRTC, so will reduce available torque a bit more, and also affect low ratio, unlike the HRTC.  Being modified downstream of the transfer box output shaft, they also screw up speedo calibration.  They are, however, the cheapest method.

I have an overdrive behind my standard(ish) SIII transmission and Tdi.  I did fit SII Suffix B low range gears to my transfer box which drop low range by about 17% compared to subsequent units, which allows more torque or less strain on the gear box.  Overdrive is still a little low geared behind a Tdi on 7.50 or 235/85 tyres, so I have bought some 4.1:1 final drive (diff) gears to raise the overall gearing a little.  I found 3.54 diffs from coiler vehicles too tall for my liking.